Processing and use of Alocasia macrorrhiza (taro) roots
for fattening pigs under mountainous village
conditions
Pham Sy Tiep, Nguyen Van Luc and Dang Hoang
Bien
National Institute of Animal Husbandry, Hanoi,
Vietnam
Abstract
The objectives of the study were to determine the optimum processing method to reduce calcium oxalate content in Alocasia macrorrhiza roots, and to evaluate the root meal processed by the different methods in the diets of F1 growing pigs in mountainous household conditions. Alocasia macrorrhiza (AM) roots were chopped into 3mm thick pieces, and then soaked in solutions of rice-water, sodium hydroxide (NaOH) or acetic acid for 24 hours. The ratio of chopped roots : solution (kg : litre) was 1 : 1.5. Then the chopped roots were sun-dried, with 2 kg chopped roots / m2, and ground by hand.
The time for sun-drying the pieces of root soaked in NAOH and acetic acid solution was only 2.8 and 2.9 days, respectively, while sun-drying the fresh roots without soaking took 4.1 days. Soaking the chopped AM roots reduced the content of calcium oxalate by 68.7 - 74.9%. In the feeding trial AM root meal was included at 50% of the DM in diets for F1 growing pigs, replacing a mixture of maize meal and soybean meal. Dry matter intake and daily gains were significantly increased, and feed conversion improved in the diets containing the soaked AM root meal compared to drying only.
It can be concluded that after processing, the Alocasia macrorrhiza root meal can be included at levels of up to 50% in the diets of growing pigs.
Key words: Alocasia macrorrhiza roots, acetic acid,
calcium oxalate, F1 growing pigs, rice-water, soaking, sodium hydroxide, sun-drying.
Introduction
More efficient use of local feed resources and improving the
economical efficiency of pig production are major goals of animal
production in the northern mountainous areas of Vietnam.
Alocasia macrorrhiza, or Taro, grows wild on mountain
slopes and is mainly planted in the gardens in villages in
highlands of northern Vietnam. Alocasia macrorrhiza (AM) is
thus a cheap, locally available feed resource, but is little used
because of its itching characteristic, which is due to a high
content of calcium oxalate. Few studies have been carried out on
processing techniques to reduce its calcium oxalate content.
AM roots are rich in starch and some minority groups have used
the stems and leaves of AM as a vegetable for feeding pigs for a
long time. Gerpacio and Castillo (1998) reported that the fresh AM
root has the following chemical composition: dry matter 26.7%;
crude protein 2.10%; crude fiber 1.40%, NFE 21.6%, ash 1.30%,
Ca 0.12 % and P 0.09%. Studies have shown that the calcium oxalate can be
released when the cellular structure of the root is
disrupted by chopping, grinding, and then soaking in NaOH or acid
solutions. After drying or cooking the AM roots can be used for pig
feed.
The aims of this study were to determine the best
processing method to reduce calcium oxalate content in Alocasia
macrorrhiza roots, and to evaluate the root meal in diets for F1
growing pigs in mountainous household conditions.
Materials and Methods
The two experiments were carried out in Cho Chu Village, Dinh
Hoa district, in Thai Nguyen province.
Experiment 1: Effect of different processing
methods of Alocasia macrorrhiza roots on calcium oxalate
concentration
The experiment was conducted in households in Cho Chu Village.
Alocasia macrorrhiza (AM) root meal was produced by the
following steps:
-
Fresh AM roots were washed clean of soil.
-
The roots were sliced into 3mm thick chips.
-
The chips were soaked in the different solutions for 24 hours.
-
Finally, the chips were sun-dried and ground by hand.
|
Table 1. Details of processing techniques prior to sun-drying |
||||
|
|
Treatment |
|||
|
Parameter |
DR |
RW |
NH |
AA |
|
Processing method |
None |
Soak in rice- water |
Soak in NaOH solution |
Soak in acetic acid solution |
|
Concentration of solution (w/v) |
- |
- |
3% |
3% |
|
Ratio chips/solution (kg: litre) |
- |
1:1.5 |
1:1.5 |
1:1.5 |
|
Soaking duration (hours) |
- |
24 |
24 |
24 |
|
Sun-drying duration (days) |
3-4 |
2-3 |
2-3 |
2-3 |
The chemical composition of the AM root meal was determined before and after processing. Samples were analysed for dry matter, crude protein, crude fat, Ca, P and calcium oxalate (mg/kg) according to AOAC (1990) procedues.
Experiment 2: Effects of
different processing methods of Alocasia macrorrhiza (AM)
root meal on the feed intake and growth performance of F1
growing pigs
The experiment was carried out in small farms in Cho Chu Village
as a completely randomized block design. Forty crossbred
F1(Yorkshire x Mong Cai) pigs with initial body weight of 20.0
± 1.0 kg were divided into two households, with 20 pigs per
household and with each household as block. The pigs in each
household were allocated randomly into 5 pens (treatments), with 2
pigs (1 male + 1 female) per pen. The animals were fed ad
libitum during the experimental period to determine total and
daily feed intake. Drinking water was freely available from
automatic drinkers.
Experimental treatments
The treatments were:
-
DR: Dried root meal (not soaked)
-
RW: Dried root meal, after soaking roots in rice washing water
-
NH: Dried root meal, after soaking roots in sodium hydroxide
-
AA: Dried root meal, after soaking roots in acetic acid
-
CTRL: A traditional diet consisting of maize, rice bran, soybean meal, limestone, salt and a mineral/vitamin mixture (Table 2).
|
Table 2. Ingredient and chemical composition of experimental diets |
|||
|
|
Price(VND/kg) |
AM root diets |
Control diet% DM basis |
AM root meal |
1000 |
50.0 |
0 |
Maize meal |
2400 |
10.0 |
25.0 |
|
Rice bran |
1300 |
13.0 |
53.0 |
|
Soybean meal |
6000 |
25.0 |
20.0 |
|
Vit-min premix |
40 000 |
0.5 |
0.5 |
|
Salt |
1500 |
0.5 |
0.5 |
|
Limestone |
1000 |
1.0 |
1.0 |
|
Total (%) |
|
100 |
100 |
|
Nutritive value |
|
|
|
|
ME (Kcal / kg) |
|
2972 |
2968 |
|
CP (%) |
|
15.1 |
15.2 |
|
Price per kg feed (VND) |
|
2627 |
2827 |
During the experimental period all diets were given 3 times per
day. Banana stems were provided at 1.5 - 2.0
kg/pig/day depending on the age of the pigs. Feed offered and feed
refusals were recorded daily. At the beginning and at the end of
each feeding period the pigs were weighed in the morning before
feeding. When the pigs reached a body weight of around 50 kg, the
experiment was stopped, and 4 pigs (2 pigs from AM and 2 pigs from
control pens) were slaughtered to test for meat quality. Parameters
determined were as shown below:
-
Daily feed intake
-
Average daily gain
-
Feed conversion ratio
-
Animal health.
-
Quality of meat in terms of colour, smell, carcass % of live weight, lean meat % in carcass.
-
Economical efficiency.
Data analysis
The data were analyzed using the GLM option of the
ANOVA software in MINITAB
program 11.2.
Results and discussion
Experiment 1
The time required for sun-drying the AM chips depended on the
solution used (Table 3). The chips soaked in NAOH and acetic acid solutions only
required 2.8 and 2.9 days, respectively, while chips that had not been soaked
required 4.1 days of sun-drying. There were no clear differences between the
four treatments in the chemical composition of the AM meal, except for the
content of calcium oxalate. Drying reduced the content of calcium oxalate by
51.7% compared to the fresh roots, and soaking reduced oxalate by
from 68.7 to 74.9% (P<0.05). An explanation for this can be that
during soaking the resin on the surface was dissolved in the solutions
and due to osmotic pressure, the oxalate was leached out from the
chips and neutralized by the respective solutions.
|
Table 3. Chemical composition of fresh and processed AM roots |
|||||
|
|
Fresh |
DR |
RW |
NH |
AA |
|
Duration of sun-drying (days) |
- |
4.1a |
3.2ab |
2.8b |
2.9b |
|
Dry matter (%) |
25.7 |
85.8 |
86.5 |
86.2 |
85.9 |
|
Composition DM basis |
|||||
|
Crude protein (%) |
7.7 |
6.3 |
6.8 |
6.5 |
6.8 |
|
Crude fat (%) |
3.1 |
1.7 |
2.0 |
2.0 |
2.0 |
|
Crude fiber (%) |
3.1 |
3.2 |
3.3 |
3.1 |
3.5 |
|
Ca (%) |
0.3 |
0.4 |
0.4 |
0.3 |
0.4 |
|
P (%) |
0.91 |
1.6 |
1.5 |
1.4 |
1.9 |
|
Calcium oxalate (mg/kg) |
113a |
44.3b |
32.1bc |
22.2c |
30.8c |
|
abcMean values within rows without common superscript are different at
p<0.05 |
|||||
Figure 1: Effect of sun-drying, or
soaking in rice water, acetic acid or sodium hydroxide
on calcium oxalate content of the roots of
Alocasia macrorrhiza
Experiment 2
There were no health problems observed in the
experimental pigs during the trial. There were no differences in net feed
intake among the control and soaking treatments , but
intake of the diet containing the dried roots (not soaked) was
significantly lower (P<0.05) (Table 4).. Similarly, daily live weight gains
were significantly higher, and feed conversion ratios lower
(P<0.05), for treatments CTRL, NH and AA compared to DR.
|
Table 4. Effect of Alocasia macrorrhiza root meal processed by different methods on feed intake and growth performance of growing pigs (20 - 50 kg LW) |
|||||
|
|
DR |
RW |
NH |
AA |
CTRL |
|
Live weight (kg) |
|
|
|
|
|
|
Initial |
20.7 |
20.1 |
20.2 |
20.5 |
20.3 |
|
Final |
49.6 |
50.7 |
52.2 |
51.6 |
52.3 |
|
Feed DM (kg) |
|
|
|
|
|
|
Offered |
121a |
110b |
110b |
109b |
109b |
|
Waste |
47.2 |
31.3 |
22.7 |
25.2 |
20.8 |
|
Net intake |
73.7a |
78.3ab |
87.7b |
83.4b |
88.5b |
|
Daily feed intake (g) |
1053a |
1114ab |
1253b |
1191b |
1264b |
|
ADG (g) |
413a |
437ab |
457b |
441b |
458b |
|
FCR (kg feed / kg gain) |
4.2a |
3.6ab |
3.4b |
3.5b |
3.4b |
|
abcMean values within rows without common superscript are different at
p<0.05 |
|||||
The positive effects of soaking the roots on daily gain were mainly a result of increased feed intakes due to reduction of the "itching factor" that reduces palatability (Figure 2).
Figure 2: Relationship between feed intake and growth rate
There were no differences between the NH and control treatments for carcass yield and meat content of the carcass (Table 5). This is in agreement with other studies that indicated that using taro in diets for growing pigs did not reduce the performance and meat quality (Aregheore and Tamni 2002).
|
Table 5. Effect of Alocasia macrorrhiza root meal processed by soaking in sodium hydroxide (NH) on meat quality of growing pigs |
||
|
|
NH |
CTRL |
|
Carcass (% in LW) |
72.7 |
72.2 |
|
Lean meat (% in carcass) |
55.4 |
54.8 |
Conclusions
-
Soaking the chopped Alocasia macrorrhiza roots reduced the content of calcium oxalate by 68.7 to 74.9%, with the best results obtained by soaking in a solution of sodium hydroxide.
-
The diet containing 50% Alocasia macrorrhiza roots soaked in sodium hydroxide solution supported the highest daily feed intake and growth rate and the lowest feed conversion ratio.
-
The beneficial effects of soaking the roots were manifested in higher feed intakes which explained 93% of the variation in growth rate
References
AOAC 1990 Association of Official Analytical Chemists,
Official methods of Analysis, 15th edn. Vol 1. AOAC.
Washington, DC.
Aregheore E M and Tamni E 2002 The nutritional value of
processed small whole taro corm (Colocasia esculenta) and taro
peels as energy source in concentrate supplements of does and
kids. Thai Journal of Agricultural Science.. 35:3,
309-317.
Gerpacio A L and Castillo L S 1998 Nutrient composition of some
Philippines feedstuffs. Los Banos, 12-24.